ESI FT-ICR Research Articles

Low-temperature oxidation of heavy crude oil characterized by TG, DSC, GC-MS, and negative ion ESI FT-ICR MS

Low-temperature oxidation (LTO) is of great significance for the subsequent oxidation reactions and oil recovery during in-situ combustion. The paper brings an in-depth analysis of crude oil LTO that is still not well understood. Firstly, one Xinjiang heavy oil was subjected to LTO reactions under different temperatures conducted in an oxidation reactor. The combustion behaviors of the oxidized oils were then investigated by thermogravimetry and differential scanning calorimetry. The Friedman and Ozawa-Flynn-Wall methods were adopted to perform combustion kinetic analysis of the oxidized oils. Subsequently, both gas chromatograph-mass spectroscopy and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry were introduced as a new route to investigate the compositional changes of crude oil caused by LTO. The condensation of aromatics as well as aromatization and condensation of other compounds was intensified from 40 to 200 °C. Chain saturated aliphatic, monocyclic, bicyclic, and tricyclic naphthenic acids were the main acidic components in the oxidized oils. The relative abundance of chain saturated aliphatic acids and O1 species was decreased from 40 to 200 °C, whereas that of tricyclic naphthenic acids and O3 species was increased. Finally, we summarized LTO reaction pathways of crude oil, which helped to understand LTO mechanisms.

Transformation mechanisms of organic S/N/O compounds during microwave pyrolysis of oil shale: A comparative research with conventional pyrolysis

This study conducted experiments on shale oil production with less S/N/O compounds by microwave pyrolysis of oil shale (MW) compared with conventional pyrolysis (CON). Mass balances of S/N/O elements during MW and CON were performed. Organic S/N/O compounds in shale oils were identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and their transformation mechanisms were investigated at a molecular level. Results indicate MW promoted S/N/O transform into chars and/or gases, reducing contents in shale oils by the maximum of 76.13, 13.22 and 27.86%, respectively. MW primarily facilitates rupture of CS and CN bonds and polymerization in S/N/O compounds. For S/N compounds with lower double band equivalents (DBEs), CS and CN bonds are readily to break producing H2S and NH3, while for those with higher DBEs, polymerization tends to occur. These reactions augmented the relative abundances (RAs) of S/N compounds with higher DBEs. For O2 species, however, side chains containing carboxyl group tend to fragment from aromatic rings, thus fatty acids (DBE = 1) present the highest RAs. Reaction mechanisms of S/N/O compounds during MW were proposed and discussed at a molecular lever, which would provide technical guidance for industrial applications.

Molecular characterization of transformation and halogenation of natural organic matter during the UV/chlorine AOP using FT-ICR mass spectrometry

UV/chlorine process, as an emerging advanced oxidation process (AOP), was effective for removing micro-pollutants via various reactive radicals, but it also led to the changes of natural organic matter (NOM) and formation of disinfection byproducts (DBPs). By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS), the transformation of Suwannee River NOM (SRNOM) and the formation of chlorinated DBPs (Cl-DBPs) in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination. In comparison to dark chlorination, the involvement of ClO•, Cl•, and HO• in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity (AImod) value and DBE (double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds. Meanwhile, more compounds which contained only C, H, O, N atoms (CHON) were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions. A total of 833 compounds contained C, H, O, Cl atoms (CHOCl) were observed after the UV/chlorine AOP, higher than 789 CHOCl compounds in dark chlorination, and one-chlorine-containing components were the dominant species. The different products from chlorine substitution reactions (SR) and addition reactions (AR) suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity. Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds, removed CHON compounds and enhanced the formation of Cl-DBPs. The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.

Analysis of Robusta coffee cultivated in agroforestry systems (AFS) by ESI-FT-ICR MS and portable NIR associated with sensory analysis

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI(±)FT-ICR MS) and portable micro near-infrared spectroscopy (microNIR), coupled to sensory analysis, were used to propose a new analytical methodology to observe the characteristics of Robusta coffees cultivated in agroforestry systems (AFS). Principal component analysis (PCA) chemometric models provided excellent discrimination of the samples analyzed by ESI(±)FT-ICR mass spectra for the ground coffee grains. Analysis of the spectra allowed for identification of the compounds responsible for distinguishing the samples grown with different intercropping AFS species. The microNIR results corroborated the ESI(-)FT-ICR MS data and the sensory analysis, by grouping together coffees grown in AFS intercropped with Gliricidia sepium and Inga edulis. The coupling of these analytical techniques shows promise in coffee quality control, presenting advantages such as collection at point analysis, speed, and analytical reliability.

Estimating the intermediate precision in petroleum analysis by (±)electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) is an important analytical technique used for the elucidation of crude oil polar compounds at the molecular level, providing thousands of heteroatom compounds in a single analysis. Due to the high resolution, the complexity of data produced, and steps involved in spectra acquisition and processing, it is necessary to estimate its intermediate precision. Intermediate precision was estimated for positive- and negative-ion ionization modes (ESI(±)) using Composer® software for two Brazilian crude oil samples. The analytical parameters evaluated were the class distribution histogram, the double bond equivalent (DBE) distribution, and the DBE versus carbon number. The statistical parameters used to study the intermediate precision were calculated from the average, standard deviation, confidence interval (significance level at 5%), coefficient of variation (CV), intermediate precision limit (ISO 5725), and principal component analysis (PCA). Two crude oil samples (A and B) were analyzed, in triplicate, for seven consecutive days by ESI(±) FT-ICR MS. The assigned class limit by ESI(+) for crude oil A was 0.42% (O2 S[H] class) and for crude oil B was 0.04% (N2 O2 S[H] class). The assigned DBE intensity limits for the two crude oils were 0.04% for ESI(+) and 0.013% for ESI(-). The PCA for ESI(-) and ESI(+) modes presented better precision for crude oils B and A, respectively. The most abundant classes and DBE of the majority class (i.e., with the highest intensity) are the parameters produced from the Composer® software that had the highest precision and can be used to estimate crude oil properties. The DBE values presented lower intermediate precision limit values (0.04%) than the assigned class values (0.4%). According to CV and PCA, ESI(+) was more precise for crude oil A (83% precision) and ESI(-) for crude oil B (84% precision).

Structural Analysis of Neutral Nitrogen Compounds Refractory to the Hydrodenitrogenation Process of Heavy Oil Fractions by High-Resolution Tandem Mass Spectrometry and Ion Mobility–Mass Spectrometry

This study aims to identify and characterize compounds refractory to hydrodenitrogenation (HDN). The efficiency of a vacuum hydrocracking unit in removing nitrogen-containing compounds to produce a low-nitrogen-content effluent is examined. Molecular, structural, and compositional knowledge is a requisite for the optimization development of the hydrotreatment step processing unit because changes in the chemical composition of petroleum have a direct impact on physical properties and, thus, overall vacuum gas oil (VGO) upgrading processes. Two samples, a VGO and a effluent obtained after the HDN process containing 10 wppm of N, were analyzed by negative-mode electrospray ionization ultra-high-resolution tandem mass spectrometry (ESI–FT-ICR) and ion mobility spectrometry–mass spectrometry (IMS–MS). FT-ICR mass spectrometry provides ultrahigh mass resolving power to separate and characterize compounds in the highly complex petroleum samples. The fragments generated by MS/MS of selected N₁ refractory compounds were used for structural elucidation. Species with a double bond equivalent of 10 and 13, which proved to be highly refractory, were analyzed in more detail. On the other hand, the TWIMS–TOF MS measurements enabled the entire ion mobility analysis of refractory species to hydrotreatment processes. The MS/MS spectra revealed a specific pattern allowing for the identification of the molecular nucleus. Furthermore, it allowed for the understanding of the fragmentation pathways: loss of alkyl chains in the first step and opening and rearrangement of the nuclei after that. Ion mobility separation, in combination with MS/MS, allowed for the identification of the different conformations and the revealment of the typical fragments of these molecular nuclei. In particular, the ion mobility peak width indicates isomeric diversity and collision cross section (CCS) determination and provides structural information. The IMS analysis of the identified refractory precursor shows the evolution of its compounds at different processing stages and indicates that some families and structural conformations of N₁ species are more resistant to hydrotreatment. Isomers presenting low CCS values in negative mode are more resistant to HDN processes. The combination of TWIMS–TOF MS and ultra-high-resolution mass spectrometry opens exciting and promising prospects for structural determination of complex mixtures, in particular, problematic compounds in petroleum refining processes.

Diverse molecular compositions of dissolved organic matter derived from different composts using ESI FT-ICR MS

Dissolved organic matter (DOM) derived from various composts can promote significant changes of soil properties. However, little is known about the DOM compositions and their similarities and differences at the molecular level. In this study, the molecular compositions of DOM derived from kitchen waste compost (KWC), green waste compost (GWC), manure waste compost (MWC), and sewage sludge compost (SSC) were characterized by electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The molecular formulas were classified into four subcategories: CHO, CHON, CHOS, and CHONS. The KWC, MWC, and SSC DOM represented the highest fraction (35.8%-47.4%) of CHON subcategory, while the GWC DOM represented the highest fraction (68.4%) of CHO subcategory. The GWC DOM was recognized as the nitrogen- and sulfur-deficient compounds that were less saturated, more aromatic, and more oxidized compared with other samples. Further analysis of the oxygen, nitrogen-containing (N-containing), and sulfur-containing (S-containing) functional groups in the four subcategories revealed higher organic molecular complexity. Comparison of the similarities and differences of the four samples revealed 22.8% ubiquitous formulas and 17.4%, 11.1%, 10.7%, and 6.3% unique formulas of GWC, KWC, SSC, and MWC DOM, respectively, suggesting a large proportion of ubiquitous DOM as well as unique, source-specific molecular signatures. The findings presented herein provide new insight into the molecular characterization of DOM derived from various composts and demonstrated the potential role of these different compounds for agricultural utilization.

Direct sulfur-containing compounds analysis in petroleum via (+) ESI FT-ICR MS using HBF4 as ionization promoter

Molecular-level characterization of sulfur-containing compounds has attracted particular attention due to its relative high abundance and negative impact on the refining process. In this paper, a novel analytical method for selective ionization of sulfidic and/or isolated thiophenic compounds (thiophene rings that are not condensed with aromatic systems) and condensed thiophenic compounds (thiophene rings that are condensed with aromatic systems, DBE ≥ 6, DBE = number of rings plus double bonds to carbon) in petroleum samples was developed by using fluoroboric acid (HBF4) as ionization promoter. Positive-ion electrospray ionization [(+) ESI] Fourier transform ion cyclotron resonance mass spectrometry was followed to characterize the molecular composition. Sulfidic and/or isolated thiophenic compounds were mainly ionized as protonated molecular ions ([M+H]+), while condensed thiophenic compounds (DBE ≥ 6) were mainly ionized as molecular radical cations (M+). The method was validated by various sulfur-containing model compounds and then applied to vacuum gas oil, crude oil and heavy oil samples. (+) ESI coupled with HBF4 additive is a simple method for selective ionization of sulfides and thiophenes in high-sulfur-content petroleum samples and has the potential for the characterization of sulfides and thiophenes in other complex mixtures.

Molecular characterization of root exudates using Fourier transform ion cyclotron resonance mass spectrometry

The release of root exudates (REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa (Medicago sativa L.), bean (Phaseolus vulgaris L.), barley (Hordeum vulgare L.), maize (Zea mays), wheat (Triticum aestivum L.), ryegrass (Lolium perenne L.) and pumpkin (Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The combination of positive ion mode (+ESI) and negative ion mode (-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in +ESI mode, while aromatic compounds with high O/C were readily ionized in -ESI mode, and only 38% of the total assigned formulas were shared by -ESI and +ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS.

Molecular Characterization of Soluble Components in the Lignite by Sequential Solvent Extraction via Continuously Reducing Particle Size.

A lignite was subjected to sequential solvent extraction via continuously reducing particle size from around 20 to more than 200 mesh. Five sets of n-hexane and methanol extracts from the particles were characterized by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography–mass spectrometry. The total extract yield for lignite when using hexane and methanol as solvents could reach to 0.98 and 15.12%, respectively. The results showed that more molecules with a similar structure but different composition could be extracted by continuously reducing the particle size of the residues, indicating the nonuniform distribution of the low-solubility molecules trapped in the coal particles. The extracts were abundant in branched long-chain aliphatic moieties and oxygen-containing compounds. With the increasing of the extraction degree, the content of alkanes in the extracts decreased rapidly. On the contrary, the content of the compounds with higher condensation and more oxygen atoms increased. It should be noted that polycyclic aromatic hydrocarbons were almost steadily present in all the extraction steps. The molecular composition and distribution of organic molecules in the lignite provide clues to the understanding of coal structure, which is significant for the environmental emission and development of processing techniques for the clean and high value-added utilizations of such a low-rank and abundant coal resource.

Metabolic profiling of different wild and cultivated Allium species based on high-resolution mass spectrometry, high-performance liquid chromatography-photodiode array detector, and color analysis.

Many plants of the genus Allium are widely cultivated and consumed for their nutraceutical and health-enhancing bioactive components effective in many metabolic and infectious diseases. In particular, Allium sativum L. (garlic), the most economically important Allium species, is known to present volatile, comparatively polar sulfur-containing compounds responsible for both the typical garlic aroma and antimicrobial property. More recently, the (moderately) polar portion of garlic metabolome, rich of polyphenols and amino acids, is gaining increasing interest as a source of antioxidants and primary nutrients. In this study, we have explored the chemical diversity of eight different hydroalcoholic extracts obtained by microwave-assisted extraction of white and red crop A. sativum and wild Allium triquetrum, Allium roseum, and Allium ampeloprasum, all originating from the Mediterranean Basin. The aim is to appraise their potential dietetic and healing value through an in-depth chemical characterization and contribute to preserve and exploit natural resources. The multimethodological method applied here is based on an untargeted metabolic profiling by means of high-resolution electrospray ionization Fourier-transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry. More than 850 by ESI(+) and 450 by ESI(-) putative metabolites have been annotated covering all main classes of primary and secondary metabolites, including amino acids, alkaloids, organic and fatty acids, nucleotides, vitamins, organosulfur compounds, and flavonoids. The pigment and polyphenol components have been separated and quantified by a targeted chromatographic high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and CIEL*a*b* colorimetric assay, showing characteristic yellow and red components in each extract, related to a different milieu of anthocyanins and flavonoids as assigned by high-resolution mass spectrometry (MS).

Structural variation of humic-like substances and its impact on plant stimulation: Implication for structure-function relationship of soil organic matters

Here, five aromatic monomers, one bearing a long alkyl chain [3-pentadecylphenol (3-PP)], the second bearing a polycyclic aromatic hydrocarbon [dihydroxynaphthalene (DHN)], the third bearing an organic amine [l-3,4-dihydroxyphenylalanine (l-DOPA)], the fourth bearing a carboxylic acid [vanillic acid (VA)], and the fifth bearing a phenol [catechol (CA)] were oxidatively coupled to produce four humic-like substances (3-PP, DHN, l-DOPA, and CAVA products) to mimic the diverse organic architectures of natural humus. Analysis using several methods, including SEM, EPR, elemental analysis, FT-IR-ATR, 13C NMR and anti-oxidant capability, revealed that each of the monomeric structures was well incorporated into the corresponding humic-like substances. Seed germination acceleration and NaCl-involved abiotic stress resistance of Arabidopsis thaliana were then tested to determine whether the different structures resulted in different levels of plant stimulation. The l-DOPA, CAVA and DHN-based materials showed enhanced stimulatory activities compared with no treatment, whereas the effects of the 3-PP-based materials were meager. Interestingly, high-resolution (15 T) ESI FT-ICR mass spectrometry-based van Krevelen diagrams clearly showed that the presence of molecules with H/C and O/C ratios ranging from 0.5 to 1.0 and 0.2 to 0.4, respectively, could be connected with such biological actions. Here, the l-DOPA sample showed the highest content of such molecules, followed by the CAVA, DHN and 3-PP samples. Next, the ability of l-DOPA and CAVA products to induce resistance in A. thaliana to a pathogen-related biotic stress was tested to confirm whether the proposed molecular features are associated with multi-stimulatory actions on plants. The expression level of pathogenesis-related protein 1 and inspection of plant morphology clearly revealed that both the l-DOPA and CAVA products stimulate plants to respond to biotic stresses. Size-exclusion chromatography together with NMR and IR data of both the materials strongly suggests that lignin-like supramolecular assemblages play an important role in versatile biological activities of humus.

New Insights on Organic Geochemistry Characterization of the Putumayo Basin Using Negative Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Biomarkers are fossil organic molecules that contain information about either the precursor organisms or the environmental conditions that generated petroleum. They become useful tools to establish stratigraphic correlations, assess the depositional environment and even check the history of the organic matter. High resolution mass spectrometry (FT-ICR MS) is considered nearly indispensable when nitrogen, oxygen or sulfur containing (NSO) biomarker compounds need being explored. In this contribution, we present an integrated study performed over thirty-three crude oils from Putumayo Basin, Colombia. Based on GC-MS traditional analysis we provide an interpretation outline built on classic hydrocarbon biomarkers. These outcomes allowed stablishing no biodegradation in most of the samples. Samples were grouped based on whether the ratio Pr/Ph was higher or lower than one, and further correlated with the abundance of oxygen compounds (classes O1 and O2) detected by ESI (-) FT-ICR MS. In addition, saturate biom...

Contribution of ketone/aldehyde-containing compounds to the composition and optical properties of Suwannee River fulvic acid revealed by ultrahigh resolution mass spectrometry and deuterium labeling.

A prior method of mass labeling ketone-/aldehyde-containing species in natural dissolved organic matter (DOM) is further developed and applied. This application involved the treatment of Suwannee River fulvic acid (SRFA) with increasing concentrations of sodium borodeuteride (NaBD4), followed by detection of reduced species via negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). The extent of reduction, as determined by ESI FTICR MS, resulting from increasing concentrations of NaBD4 correlated well with changes in the absorption and emission spectra of the corresponding untreated and borodeuteride-reduced samples, providing evidence that ketone/aldehyde functional groups contribute substantially to the bulk optical properties of SRFA. Furthermore, the differences in the reactivity and abundance of ketone-/aldehyde-containing species for various regions in Van Krevelen plots were revealed, thus showing how this mass labeling method can be used to provide more detailed structural information about components within complex DOM samples than that provided by the determination and analysis of molecular formulae alone. Graphical abstract.

Assessing raw materials as potential adsorbents to remove acidic compounds from Brazilian crude oils by ESI (-) FT-ICR MS.

The presence of acidic compounds as naphthenic acids in crude oil causes several problems for the petroleum industry, including corrosion in both upstream and downstream production processes. Based on this scenario, the main objective of this work was to investigate the removal of the acidic compound from two Brazilian heavy oils by adsorption processes using six potential adsorbents: powdered shale, activated carbon, bentonite, silica gel, powdered sandstone and powdered wood. These raw materials were previously characterized by conventional and surface analysis techniques, which show that they offer a good surface area and thermal stability. To evaluate the removal efficiency at the molecular level, the crude oil samples and the filtered oils were analyzed by negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry [ESI (-) FTICR MS]. The O2 class, which is related to the relatively high acidity of the samples, was the most abundant in both crude oil samples, moreover, this class was more retained by adsorbents. Silica gel, activated carbon and bentonite were the best adsorbents of acidic compounds from the tested oils, in agreement with their markedly higher surface area and porous volume. Additionally, a chromatographic analysis was performed and showed no changes in the oil profile.

Geochemical Investigation of Tar Balls Collected in a Brazilian Beach Using Biomarkers, Ni/V, δ13C Ratios and Ultra-High Resolution FT‑ICR Mass Spectrometry

Representative tar balls collected in two distinct years (2012 and 2014) in a beach along the State of Bahia, northeastern Brazil, were geochemically characterized in order to identify correlations between them and investigate potential sources. Terpanes and steranes biomarkers (detected by gas chromatography coupled to mass spectrometry, GC-MS), carbon stable isotope ratio (δ13C), Ni and V ratios and polar compounds by Fourier transform ion cyclotron resonance mass spectrometry using electrospray ionization in negative mode (ESI(-) FT-ICR MS) were evaluated. Three Brazilian oil samples from distinct sources were assessed as possible spill sources, comparing their results with the tar ball samples. Using chemometric techniques, it was verified correlation between the two set of tar ball samples, suggesting same source. However, no correlation with the oil samples was observed, with different geochemical profile among them. The heteroatom class distribution displayed severe degradation levels for tar balls and its seems that photo-oxidation and biodegradation processes were further relevant. Tar ball samples show multiple classes, most oxygenated, and with one sample showing considerable relative abundance of N1 class, suggesting it is from a more recent oil spill. In brief, our results suggest that the region, with very sensitive ecosystem, is possibly subjected to frequent spills from the same source.

Molecular insights into the transformation of dissolved organic matter during hyperthermophilic composting using ESI FT-ICR MS

The aim of this work was to study the molecular compositional changes of dissolved organic matter (DOM) during hyperthermophilic composting (HTC) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry. Our results reveal that DOM in hyperthermophilic compost mainly consisted of lignins/carboxylic-rich alicyclic molecules (72%) with relatively lower H/C (1.24), and the higher double bound equivalent (5.98) and aromaticity index (0.22) when compared with the DOM in composting materials, suggesting that HTC led to an increase in carboxyl-rich, unsaturated, and aromatic compounds. Profiles of the DOM’s transformation indicated that low O/C (O/C < 0.3) and high H/C (H/C < 1.5) compounds were preferentially decomposed in the hyperthermophilic phase of HTC. Abundant produced intermediates, such as lignin phenols and amino sugars, were further transformed to refractory humic substances. This investigation extends the current understanding of the molecular mechanisms on humification of HTC, and reveals further applications for hyperthermophilic compost.

Characterization of organosulfur compounds in asphalt cement samples by ESI(+)FT-ICR MS and 13C NMR spectroscopy

Herein, it is presented a methodology for the characterization of organosulfur compounds in asphalt cement (AC) samples employing solid-phase extraction (SPE) associated with methylation reactions and positive-ion mode electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI(+)FT-ICR MS) and carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. Three AC samples were submitted to an SPE separation, and the fractions obtained the original AC samples, and their maltenes were methylated and analyzed using the ESI(+)FT-ICR MS. The ESI(+)FT-ICR MS ionized the sulfur fractions much better than the original samples, detecting organosulfur compounds with a broader average molecular mass distribution (Mw). Several types of sulfur compounds were detected, such as sulfides, disulfides, thiophenes, and dibenzothiophenes. Besides, the ESI(+)FT-ICR data were compared with the 13C NMR (from model molecules analyses) and ESI(+)-Orbitrap MS. The organosulfur chemical profile was correlated to the physical properties of AC samples. It was verified that the samples with higher aromatic-character were less susceptible to aging test, while the one with more saturated-character presented more significant variation in their physical properties after the aging test.

Evaluation of the effects of the simulated thermal evolution of a Type-I source rock on the distribution of basic nitrogen-containing compounds

Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allows the molecular-level characterization of ultracomplex mixtures such as crude oil samples. By combining FT-ICR MS with electrospray ionization, a myriad of polar compounds can routinely be identified and assigned with unmatched mass resolution and accuracy. The profile of polar compounds containing NSO atoms can be used to track and evaluate important parameters of crude oil. Recently, using ESI FT-ICR MS in the negative mode (https://doi.org/10.1016/j.orggeochem.2017.10.004), we investigated changes in the profile of polar compounds as a function of thermal maturity. Sulfur-containing compounds are completely destroyed during maturation, and the relatively high content of O-containing compounds decreases via decarboxylation and dehydration. The number of double bond equivalents (DBE) increased, indicating the occurrence of aromatization and condensation. However, the carbon number distribution shifted to lower values as a function of thermal maturity. Six regressions based on changes in the contents of O2 compounds were proposed as maturity parameters. Here, by focusing on tracking and evaluating the impact of thermal maturity on basic polar compounds, a set of hydrous pyrolysis (HP) products was analyzed using an ESI(+) 7.2 T LTQ FT-ICR MS system. The samples at various stages of maturity consist of one immature bitumen (original sample), eleven expelled oil samples and eight residual bitumen samples. Determining the changes in the contents of N- and NO-containing compounds with maturity allows us to propose new parameters for assessing thermal maturity that cover the full window of oil generation.

Controlling the quality of grape juice adulterated by apple juice using ESI(-)FT-ICR mass spectrometry

Food quality control is undoubtedly a process of great importance. The technological development of the last years has increased the food production and consumption, thus generating, an enormous demand for the food quality control. Grape juice is a very tasty and high quality nutraceutical drink, being widely consumed worldwide. This product has a high commercial value, making it source of several types of fraud, such as other juices' addition, like apple juice. Through negative-ion mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, it was possible to detect and quantify apple juice in integral grape juice. In this study, we used the univariate linear regression model using mixtures of integral grape juice with various concentrations of integral apple juice (0, 1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 100 wt%). The model showed good accuracy. In addition, eleven commercial samples of grape juice were tested, and in two of them, apple juice was detected at ≈25 wt%.